Known overvoltage arresters are constructed of a stack of cylindrical varistors which are arranged coaxially with respect to each other in a housing of insulating material. The individual varistors are surrounded by mutually overlapping protective elements between which and the partition wall of the housing of insulating material an annular space has been left. Although ionized gases produced, for example, by glow discharges between adjacent varistors cannot enter the annular space between the protective elements and the housing of insulating material in this overvoltage arrester, an arc can form in this space in the case of a disturbance, which arc subjects the housing of insulating material to considerable mechanical and thermal stress.
From U.S. Pat. No. 4,100,588 an overvoltage arrester is also known which comprises a stack of varistors located in a housing of insulating material, between which stack and the inside wall of the housing of insulating material bodies of silicone rubber insulating material with a filling of aluminum oxide powder are arranged. Although heat generated in the varistors is removed to the outside via the bodies of insulating material during operation of this overvoltage arrester, an arc formed in the case of a disturbance will, nevertheless, subject the housing of insulating material to considerable stress even in this overvoltage arrester.
In the case of an overvoltage arrester described in German Auslegeschrift No. 1 28 01 666 and comprising a varistor stack located inside a housing of insulating material, an annular space located between the inside wall of the housing of insulating material and the varistor stack is filled with a liquid and/or granular filling material. As a result of this feature, the housing of insulating material will selectively fall apart in the case of a disturbance and a possible exploding of the housing of insulating material is avoided in this manner.